Toward the end of 1935, legendary A&R man John Hammond was contracted by Parlophone Records to produce a series of American jazz performances that were to be released in Great Britain. Parlophone arranged for Decca Records to record the sessions in New York. [And also, in Chicago for Volume 2, with Stacy and Krupa recording in Chicago, whereas Berigan recorded in New York]. As usual, Hammond assembled hand-picked groups and chose the tunes for them to record.
The records for this set were originally issued in England. In 1941, the American Decca record company, which produced the records and still retained rights to them, reissued them as part of a six record set entitled "Gems of Jazz."
So, it was a contract between Parlophone and John Hammond, with the facilities of the Decca studios used to record the tunes by artists chosen by Hammond. Basically, what John was telling us.
Problem solved. Thanks to all who contributed.
My original error was to assume, because of the connections between Parlophone and Columbia, that the Gems of Jazz sets were recorded in the Columbia Studios. They were in fact waxed in the Decca studios.